Worldwide overview of reproduction, juvenile collection, spat production and cultivation of pen shells

Pen shells hold some potential for cultivation, but information on aquaculture activities is fragmentary, and no sustained or commercial production of any such species is currently in place. We reviewed information available worldwide on reproductive cycles, wild juvenile collection, spat production in hatcheries and cultivation systems for 45 pen shell species. We found information on the topics of interest for 15 species, Atrina maura and Atrina pectinata being the most studied. Reproductive cycles have been described for ten species, but size at first maturity has been reported only for A. maura and Pinna rugosa. Onion mesh bags and mosquito nets are the materials used for wild juvenile collection of most species. Nevertheless, seed collection has decreased for some species because of overexploitation, diseases or trawling that has severely impacted populations, so spat production in hatcheries is a fundamental aspect. Yet, hatcheries face challenges due to the high mortality of umbo larvae and during metamorphosis, and larvae produced by broodstock with overmature gonads. Market size individuals can be produced using culture methods currently available, but hatchery protocols and culture devices must be tailored specifically for pen shells. Reduced availability of wild spat and limited spat production in hatcheries are major constraints for developing and sustaining cultures. Studies on reproduction and spat production are necessary, as well as the implementation of protection measures and development of restoration plans for pen shell populations. Apparently, there is insufficient information available to foster the development of aquaculture, with tensions between preserving species and aquaculture programmes.